BTW: couldn't find an array holding the values of $1,$2,... in the perldocs !?!

Probably not much help in this particular case (and you still need to loop to capture), but 5.10 offers the %+ and %- predefined hashes for named captures (see perlvar) in place of an array of all capture groups:

>perl -wMstrict -le
"my $s = '12ab34cd56ef78';
 my @pairs;
 push @pairs, [ $+{A}, $+{B} ]
   while $s =~ m{ (?<A>[[:alpha:]]) (?<B>[[:alpha:]]) }xmsg;
 use Data::Dumper;
 print Dumper \@pairs;
"
$VAR1 = [
          [
            'a',
            'b'
          ],
          [
            'c',
            'd'
          ],
          [
            'e',
            'f'
          ]
        ];
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